1. Field of the Invention
The present invention relates to a tri-frequency duplexer circuit and multi-frequency duplexer circuit; in particular, the present invention relates to a tri-frequency duplexer circuit and multi-frequency duplexer circuit utilizing mushroom Electromagnetic Band Gap (EBG) frequency designs.
2. Description of Related Art
At present, system integration technologies have made huge contributions to the advancement of the wireless system, and wireless communication systems capable of integrating a variety of communication frequency specifications have especially become the focused issue recently as well. Therefore, the circuit design at the system integration end whose circuits enable good integration of various functions in accordance with different communication specifications is definitely one of the best technologies in such type of focused application fields.
Common circuit designs may include the duplexer, the diplexer and the triplexer. FIG. 1-a shows a duplexer, FIG. 1-b shows a diplexer, and FIG. 1-c shows a triplexer. Though conventional technologies can integrate different communication specifications, including the bi-directional communication in the duplexer 100, as well as the frequency classification function in the diplexer 101 and the triplexer 102, current microwave circuit at the integration end can nevertheless only achieve either bi-direction communication or frequency classification function. In other word, a bi-directional communication circuit is incapable of providing frequency classification function, while the circuit having frequency classification function does not provide bi-directional communication. The reasons for this dilemma found in the present microwave circuit lie in limitation of prior art design and use of non-comprehensive matching network. Consequently, seeking alternative design solutions to allow the microwave circuit at the integration end to simultaneously have bi-directional communication and frequency classification function will be helpful for the construction of future integrated communication systems.